...and finally, this isn't all theoretical stuff. If you look at some of the best images going around, including this recent one by Chris Go:
http://www.cloudynights.com/ubbthrea...270619-37c.jpg
taken with a C11, it's quite evident that detail much smaller than the airy disk size is visible. In particular if you look at the white storm in the upper right of the image, to the right of the (now red) oval BA, this white storm is approximately 0.3 arc seconds across (smaller than the airy disk size for a C11), and yet it is clearly resolved, including a distinct dark edge. Looking around the image shows many features much smaller that are also partially or fully resolved!
regards, Bird